Noise suppression circuit and air conditioning equipment

Abstract

The utility model provides a noise suppression circuit and air conditioning equipment, and the noise suppression circuit comprises a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; the input end of the first voltage sampling module receives input voltage, and the first noise module works according to the input voltage; the first voltage sampling module detects a first sampling voltage signal of the first noise module and sends the first sampling voltage signal to the current compensation module through a signal end of the first voltage sampling module; the first equivalent impedance module provides a first resistance signal equivalent to the resistance value of the first noise module for the current compensation module; the current compensation module determines the current value of a first compensation current signal according to the voltage value of the first sampling voltage signal and the resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module. According to the embodiment provided by the scheme, the noise generated when the first noise module works can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of circuit, and particularly relates to a noise suppression circuit and an air conditioning equipment. BACKGROUND

[0002] The variable frequency drive system is a system for controlling the speed and torque of a motor by adjusting the frequency and voltage of power supply of the motor, and is widely used in industrial automation, building air conditioning, water pump and the like.

[0003] In the related art, in order to reduce electromagnetic interference caused by switching action of a frequency converter in a variable frequency drive system, electromagnetic interference noise generated by a power conversion device needs to be suppressed, such as using an electromagnetic interference filter to suppress the noise. However, with the increasing demand for high frequency, miniaturization and cost reduction of the variable frequency drive system, the disadvantages of large size, large weight, high cost and large high-frequency bandwidth affected by a magnetic sensor of the filter are gradually prominent. CONTENT OF THE INVENTION

[0004] The embodiments of the present application provide a noise suppression circuit and an air conditioning equipment, which can reduce noise generated by a noise source, and reduce the size, complexity and cost of the noise suppression circuit. The above technical solutions are as follows:

[0005] In a first aspect, the embodiments of the present application provide a noise suppression circuit, which comprises:

[0006] a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module;

[0007] The input end of the first voltage sampling module receives an input voltage, the input end of the first noise module is connected with the input end of the first voltage sampling module, and the first noise module works according to the input voltage;

[0008] The output end of the first noise module is connected with the output end of the first voltage sampling module, the signal end of the first voltage sampling module is connected with the signal end of the current compensation module, the first voltage sampling module detects a first sampling voltage signal of the first noise module, and sends the first sampling voltage signal to the current compensation module through the signal end of the first voltage sampling module;

[0009] The input end of the first equivalent impedance module is connected with the output end of the first voltage sampling module, and the output end of the first equivalent impedance module is connected with the input end of the current compensation module, the first equivalent impedance module provides a first resistance signal with a resistance value equivalent to that of the first noise module for the current compensation module;

[0010] An output end of the current compensation module is connected with an input end of the first noise module, and the current compensation module determines a current value of a first compensation current signal according to a voltage value of the first sampling voltage signal and a resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module to reduce the noise generated by the first noise module when working.

[0011] In a second aspect, the embodiments of the present application provide an air conditioning device, which comprises the noise suppression circuit provided by the first aspect or any possible implementation manner of the first aspect.

[0012] The noise suppression circuit provided by the embodiments of the present application comprises a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module. The noise voltage generated by the first noise module is captured by the first voltage sampling module to generate a first sampling voltage signal. The first equivalent impedance module provides an equivalent impedance signal according to the working characteristics of the first noise module. Then, the first sampling voltage signal and the first resistance signal are transmitted to the current compensation module. The current compensation module obtains a first compensation current signal according to the two signals. The size and direction of the first compensation current signal are accurately adjusted, which can be opposite to the direction of the noise current. By injecting a current opposite to the direction of the noise current into the first noise module, the corresponding current compensation can be performed before or at the initial stage of the noise generation, thereby effectively reducing the noise generated by the first noise module. In an ideal case, the size of the first compensation current signal is equal to that of the noise current, and the direction of the first compensation current signal is opposite to that of the noise current, so that the effects of the two currents can be offset to completely eliminate the noise current. Thus, the noise generated by the first noise module when working can be effectively reduced or eliminated. In addition, compared with the traditional noise suppression method which relies on a current transformer to sample the current, the noise suppression circuit provided by the present application directly samples the voltage and analyzes the sampling voltage signal to calculate the current value of the corresponding current compensation signal, thereby effectively avoiding the volume and complexity problems caused by the traditional current transformer, and reducing the volume and design cost of the noise suppression circuit. BRIEF DESCRIPTION OF DRAWINGS

[0013] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0014] Figure 1 A first structure schematic diagram of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0015] Figure 2 A structure schematic diagram of an equivalent circuit of a noise suppression circuit provided by an exemplary embodiment of the present application;

[0016] Figure 3 A second structural schematic diagram of a noise suppression circuit provided for an exemplary embodiment of the present application;

[0017] Figure 4 A third structural schematic diagram of a noise suppression circuit provided for an exemplary embodiment of the present application;

[0018] Figure 5 A structural schematic diagram of a test circuit provided for an exemplary embodiment of the present application;

[0019] Figure 6 A structural schematic diagram of another test circuit provided for an exemplary embodiment of the present application;

[0020] Figure 7 A schematic diagram of common mode impedance characteristics provided for an exemplary embodiment of the present application;

[0021] Figure 8 A structural schematic diagram of a fitting circuit provided for an exemplary embodiment of the present application;

[0022] Figure 9 A structural schematic diagram of a simplified fitting circuit provided for an exemplary embodiment of the present application;

[0023] Figure 10 A structural schematic diagram of a noise suppression circuit of multiple noise sources provided for an exemplary embodiment of the present application;

[0024] Figure 11 A structural schematic diagram of an air conditioning system provided for an exemplary embodiment of the present application;

[0025] Figure 12 A schematic diagram of a first simulation result provided for an exemplary embodiment of the present application;

[0026] Figure 13 A schematic diagram of a second simulation result provided for an exemplary embodiment of the present application;

[0027] Figure 14 A schematic diagram of a third simulation result provided for an exemplary embodiment of the present application. DETAILED DESCRIPTION

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application.

[0029] The terms "first", "second", "third", and the like in the description and claims of the present application and the above drawings are used to distinguish different objects, and are not used to describe a specific order. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0030] A variable frequency drive system is a system for controlling the speed and torque of a motor by adjusting the frequency and voltage of the motor power supply, which is widely used in industrial automation, building air conditioning, water pumps and other applications.

[0031] In related technologies, in order to reduce electromagnetic interference (EMI) caused by the switching action of the frequency converter in the variable frequency drive system, it is necessary to suppress from two aspects of noise source and propagation path. In terms of noise source, it is usually to change the control strategy and modulation algorithm of the frequency converter to adjust the output voltage and current waveform, so as to reduce the strength of EMI noise. However, the change of control and modulation algorithm may affect the operating efficiency and stability of the power converter. Therefore, in addition to adjusting the control strategy, increasing the EMI filter is also a common noise suppression means, especially reducing noise propagation through the EMI filter.

[0032] Currently, EMI filters are mainly divided into passive, active and hybrid types. Passive EMI filters usually have large size, heavy weight, high cost and large loss, so their disadvantages gradually appear in the background of increasing demand for high frequency, miniaturization and cost reduction of variable frequency drive systems. This also promotes the research and application of active filters or the combination of passive and active filters to adapt to the development trend of the system. The design method of active filter usually uses current transformer (CT) or voltage transformer, but the bandwidth of CT is limited by the nonlinear characteristics of magnetic elements, high-frequency parasitic capacitance, leakage inductance and equivalent series resistance and other factors. In addition, CT needs to bear the normal working current to avoid saturation, so its size is large and the cost is high. In addition, the voltage transformer is also affected by the magnetic properties and parasitic parameters, and the system bandwidth will also be limited. Under high-power applications, the secondary winding of the voltage transformer needs to bear large current, which limits the system gain. Therefore, the design of active filter needs to balance the noise suppression effect, system stability, cost and size, etc. to meet the needs of variable frequency drive system for high frequency, miniaturization and cost optimization.

[0033] To solve the above technical problems, a noise suppression circuit is provided. Please refer toFigure 1 Figure 1 shows a first structure of a noise suppression circuit according to an embodiment of the present application. As shown in Figure 1, the noise suppression circuit comprises: Figure 1

[0034] a first noise module 11, a first voltage sampling module 12, a first equivalent impedance module 13, and a current compensation module 14.

[0035] The input end of the first noise module 11 is connected to the input end of the first voltage sampling module 12, the output end of the first noise module 11 is connected to the output end of the first voltage sampling module 12, the input end of the first voltage sampling module 12 receives an input voltage, the output end of the first voltage sampling module 12 is connected to the input end of the first equivalent impedance module 13, the output end of the first equivalent impedance module 13 is connected to the input end of the current compensation module 14, the output end of the current compensation module 14 is connected to the input end of the first noise module 11, and the signal end of the current compensation module 14 is connected to the signal end of the first voltage sampling module 12.

[0036] The first noise module 11 works according to the input voltage.

[0037] The first voltage sampling module 12 detects a first sampling voltage signal of the first noise module 11 and sends the first sampling voltage signal to the current compensation module 14 through the signal end of the first voltage sampling module 12.

[0038] The first equivalent impedance module 13 provides a first resistance signal equivalent to the resistance value of the first noise module 11 for the current compensation module 14.

[0039] The current compensation module 14 determines the current value of a first compensation current signal according to the voltage value of the first sampling voltage signal and the resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module 11 to reduce the noise generated when the first noise module 11 works.

[0040] In some embodiments, the first noise module 11 works based on the input voltage. During the working process, noise may be generated due to characteristics such as electromagnetic interference, radio frequency interference, switching noise, current fluctuation, non-linear effect, etc. This noise is manifested as high-frequency voltage or current fluctuation.

[0041] In some embodiments, the first voltage sampling module 12 collects a first sampling voltage signal generated by the first noise module 11. For example, the first voltage sampling module 12 samples the input voltage using a specific voltage sampling circuit to obtain the first sampling voltage signal, and then the first voltage sampling module 12 sends the first sampling voltage signal to the current compensation module 14 through the signal end connected to the current compensation module 14.

[0042] ​In some embodiments, the first equivalent impedance module 13 is used to provide the current compensation module 14 with the resistance characteristics of the first noise module 11. When the first noise module 11 is working, it generates certain impedance characteristics. The first equivalent impedance module 13 provides an equivalent impedance signal, namely a first resistance signal, based on the working characteristics of the first noise module (i.e., the impedance generated by the noise). This signal simulates the resistance characteristics of the noise source and is transmitted to the current compensation module 14.

[0043] In some embodiments, the current compensation module 14 calculates the current value of the first compensation current signal based on the voltage value of the first sampled voltage signal and the resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module 11 to compensate or cancel the noise signal by introducing a current with the opposite direction to the current in the first noise module 11.

[0044] Next, combine Figure 2 The noise suppression circuit provided in this application will be described. Figure 2 A schematic diagram of the equivalent circuit structure of a noise suppression circuit provided for an exemplary embodiment of this application is shown below. Figure 2 The noise voltage generated by the common-mode noise source is V. x Without the noise suppression circuit provided in this application, the noise voltage V x The influence of common-mode current I X The common-mode current flows to ground through the load unit in the first noise module 11, and its expression is: Among them, Z motor Z is the common-mode impedance between the load unit and ground in the first noise module 11. p This refers to the equivalent parasitic impedance of the midpoint of the three-phase bridge arm in the inverter unit of the first noise module 11 to ground. These common-mode currents flow through the noise detection module LISN and are detected, potentially causing noise problems.

[0045] To suppress noise, this application provides a noise suppression circuit, including a compensation network Z. s That is, the first equivalent impedance module 13, the noise suppression circuit injects a first compensation current signal I. comp To offset common-mode current I x First compensation current signal I comp Magnitude and noise voltage V x It is directly proportional, and its formula is: After the first compensation current signal is injected, it will interact with the original common-mode current I. x This counteracts the current, thereby reducing or eliminating the current flowing through the LISN. Ideally, when I... x =I comp At that time, the current I flowing through LISNLISN For zero, the effect of noise suppression is achieved. That is, by injecting a compensation current equal to and opposite to the common-mode current, the noise current can be effectively canceled out, thereby suppressing the common-mode noise of the system.

[0046] The noise suppression circuit provided by the embodiment of the present application comprises a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module. The noise voltage generated by the first noise module is captured by the first voltage sampling module to generate a first sampling voltage signal. The first equivalent impedance module provides an equivalent impedance signal according to the working characteristics of the first noise module. Then, the first sampling voltage signal and the first resistance signal are transmitted to the current compensation module. The current compensation module obtains a first compensation current signal according to the two signals, and the size and direction of the first compensation current signal are accurately adjusted. The first compensation current signal can be opposite to the direction of the noise current. By injecting a current opposite to the direction of the noise current into the first noise module, the corresponding current compensation can be performed before or at the initial stage of noise generation, thereby effectively reducing the noise generated by the first noise module. In an ideal case, the size of the first compensation current signal is equal to that of the noise current, and the direction of the first compensation current signal is opposite to that of the noise current, so that the effects of the two can be offset to completely eliminate the noise current. Thus, the noise generated by the first noise module during operation can be effectively reduced or eliminated. In addition, compared with the conventional noise suppression method relying on a current transformer for current sampling, the noise suppression circuit provided by the present application directly samples the voltage and analyzes the sampling voltage signal to calculate the current value of the corresponding current compensation signal, thereby effectively avoiding the volume and complexity problems caused by the conventional current transformer and reducing the volume and design cost of the noise suppression circuit.

[0047] Figure 3 A second structural schematic diagram of a noise suppression circuit provided by an exemplary embodiment of the present application is shown in FIG. 3. As shown in FIG. 3, the noise suppression circuit comprises a first noise module 31, a first voltage sampling module 32, a first equivalent impedance module 33 and a current compensation module 34. The connection relationship of each module is the same as that described above, and will not be described here again. Figure 3 Figure 1 The connection relationship of each module is the same as that described above, and will not be described here again.

[0048] In the embodiment, the current compensation module 34 comprises an operational amplifier unit 341, a push-pull unit 342, an adjusting resistor 343, an output resistor 344 and a voltage source.

[0049] ​The inverting input terminal of the operational amplifier unit 341 is connected with the output terminal of the first equivalent impedance module 33, the non-inverting input terminal of the operational amplifier unit 341 is connected with the ground wire, the output terminal of the operational amplifier unit 341 is connected with the input terminal of the push-pull unit 342, the output terminal of the push-pull unit 342 is connected with the first terminal of the output resistor 344, the first terminal of the adjusting resistor 343 is connected with the inverting input terminal of the operational amplifier unit 341, the second terminal of the adjusting resistor 343 is connected with the first terminal of the output resistor 344, the first pin of the operational amplifier unit 341 is connected with the positive electrode (+Vcc) of the voltage source (Volt current condenser, Vcc), and the second pin of the operational amplifier unit 341 is connected with the negative electrode (-Vcc) of the voltage source. The operational amplifier unit 341 controls the gain of the input signal (the first sampling voltage signal) through the reverse input signal and in combination with the adjusting resistor 343, so as to realize the inverting amplification of the first sampling voltage signal.

[0050] The voltage source provides a driving voltage for the operational amplifier unit 341, and the operational amplifier unit 341 and the adjusting resistor 343 perform inverting and amplifying processing on the first sampling voltage signal based on the first resistance signal to obtain an output voltage signal.

[0051] The adjusting resistor 343 is used to adjust the proportional relationship between the first sampling voltage signal as the input signal and the output voltage signal. In the current compensation module 34, the adjusting resistor 343 is connected with the inverting input terminal of the operational amplifier unit 341 and connected with the output resistor 344 to form a feedback circuit, which is used to adjust the accuracy of current compensation, so that the current compensation module 34 can accurately calculate the current value of the first compensation current signal to effectively suppress the noise through the first compensation current signal.

[0052] The push-pull unit 342 enhances the initial compensation current signal based on the output voltage signal and the output resistor 344 to obtain the first compensation current signal with a current value meeting a preset condition. Specifically, the push-pull unit 342 provides the required compensation current signal by controlling the output resistor 344 according to the output voltage signal of the operational amplifier unit 341, which enhances the compensation current to be large enough to effectively compensate the noise signal and thus meet the preset condition. Optionally, the preset condition can be that the current value of the first compensation current signal is greater than a preset threshold.

[0053] The output resistor 344 sends the first compensation current signal to the first noise module 31 through the output terminal of the current compensation module 34. The output resistor 344 is the final output part of the current compensation module 34, which transmits the current compensation signal (i.e., the first compensation current signal) to the first noise module 31. Its role is to provide a load between the current compensation module 34 and the first noise module 31 and control the characteristics of the final output current signal, so that the first compensation current signal can effectively oppose the noise signal to suppress the noise.

[0054] In this embodiment, by using feedforward control technology to perform current compensation before or at the initial stage of noise generation, the noise generated by the first noise module 31 can be significantly reduced. The current compensation module 34 can dynamically adjust the compensation current according to the sampled signal, responding to noise changes in real time, thereby achieving more accurate and efficient noise suppression. Furthermore, the current compensation module 34 performs current compensation directly through voltage sampling and signal processing, eliminating the need for traditional current transformers, reducing hardware complexity and size, and thus lowering the difficulty and cost of circuit design.

[0055] In some embodiments, such as Figure 3 The current compensation module 34 also includes a DC blocking unit 345. The first end of the DC blocking unit 345 is connected to the second end of the output resistor 344, and the second end of the DC blocking unit 345 is connected to the input terminal of the first noise module 31. Optionally, the DC blocking unit 345 can be a DC blocking capacitor. The DC blocking unit 345 can effectively isolate the DC component in the circuit, allowing only AC signals to pass through. Since DC signals may adversely affect the normal operation of the circuit, the DC blocking unit can prevent DC components from affecting the operation of the noise module, ensuring that the first compensation current signal only takes effect within the required frequency range, effectively improving the effectiveness and accuracy of the first compensation current signal.

[0056] Figure 4 A third structural schematic diagram of a noise suppression circuit provided for an exemplary embodiment of this application is shown below. Figure 4 As shown, the noise suppression circuit includes: a first noise module 41, a first voltage sampling module 42, a first equivalent impedance module 43, and a current compensation module 44. The current compensation module 44 includes: an operational amplifier unit 441, a push-pull unit 442, an adjustment resistor 443, an output resistor 444, and a DC blocking unit 445; the first terminal of the DC blocking unit 445 is connected to the second terminal of the output resistor 444, and the second terminal of the DC blocking unit 445 is connected to the input terminal of the first noise module 41.

[0057] The connection relationships of each module are as described above. Figure 3 The same applies, so I won't go into details here.

[0058] In some embodiments, the noise suppression circuit further includes a first protection module 45; the output terminal of the first noise module 41 is connected to the input terminal of the first equivalent impedance module 43 through the first protection module 45; the first protection module 45 follows the first sampled voltage signal output by the first voltage sampling module to obtain a first follow-up voltage signal with a voltage value equal to the voltage value of the first sampled voltage signal, so as to protect the first voltage sampling module 42.

[0059] In the embodiment of the present application, by generating a first follow-up voltage signal equal to the voltage value of the first sampling voltage signal, the first protection module 45 can effectively limit the excessive fluctuation of the voltage, and the first voltage sampling module 42 can continue to work normally under high voltage or abnormal voltage conditions, and will not fail due to instantaneous overvoltage or fluctuation, thereby improving the stability and reliability of the entire noise suppression circuit.

[0060] In some embodiments, the push-pull unit 442 includes a first diode D1, a second diode D2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a first triode Q1, and a second triode Q2. The output end of the operational amplifier unit 441 is connected to the negative electrode of the first diode D1, the positive electrode of the first diode D1 is connected to the first end of the first resistor R1, the second end of the first resistor R1 is connected to the positive electrode of the voltage source, the positive electrode of the first diode D1 is connected to the base of the first triode Q1, the collector of the first triode Q1 is connected to the positive electrode of the voltage source, the emitter of the first triode Q1 is connected to the first end of the second resistor R2, and the second end of the second resistor R2 is connected to the first end of the output resistor. The output end of the operational amplifier unit 241 is connected to the positive electrode of the second diode D2, the negative electrode of the second diode D2 is connected to the first end of the third resistor R3, the second end of the third resistor R3 is connected to the negative electrode of the voltage source, the negative electrode of the second diode D2 is connected to the base of the second triode Q2, the emitter of the second triode Q2 is connected to the negative electrode of the voltage source, the collector of the second triode Q2 is connected to the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is connected to the first end of the output resistor 444.

[0061] In the embodiment of the present application, the push-pull unit 442 uses two triodes (Q1 and Q2) and diodes (D1 and D2) to construct a push-pull amplification structure, and through reasonable current path distribution, the current is enhanced. In this way, the amplitude of the first compensation current signal can be large enough to meet the requirements of the noise suppression circuit for the compensation current. Moreover, the push-pull unit 442 combines the working modes of two groups of symmetrical triodes, effectively improves the power conversion efficiency of the circuit, compared with the working mode of a single triode, the push-pull unit 442 can make the current output more linear and reduce power loss, thereby optimizing the performance of the overall circuit.

[0062] In some embodiments, the first noise module 41 includes an inverter unit 411 and a load unit 412, the inverter unit 411 includes a three-phase bridge arm, and the load unit 412 includes a three-phase winding; the three output ends of the three-phase bridge arm are respectively connected to the three-phase winding; the inverter unit is used to drive the load unit to operate. Wherein, the load unit 412 can include a motor and related cables, etc.

[0063] In the embodiment of the present application, the inverter unit 411 converts the direct current power into three-phase alternating current through the three-phase bridge arm, and then drives the three-phase load unit 412. The high efficiency of the three-phase system can provide balanced current and low harmonic distortion, so that the operation of the load unit 412 is more stable and efficient.

[0064] In some embodiments, the first voltage sampling module 42 includes a first sampling resistor SR1, a second sampling resistor SR2, a third sampling resistor SR3, a fourth sampling resistor SR4, and a fifth sampling resistor SR5; the three-phase winding is connected to the first end of the first sampling resistor SR1, the first end of the second sampling resistor SR2, and the first end of the third sampling resistor SR3; the second end of the first sampling resistor SR1, the second end of the second sampling resistor SR2, and the second end of the third sampling resistor SR3 are connected to the first end of the fourth sampling resistor SR4, the second end of the fourth sampling resistor SR4 is connected to the first end of the fifth sampling resistor SR5, and the second end of the fifth sampling resistor SR5 is connected to the ground wire.

[0065] In the embodiment of the present application, the voltage of the three-phase winding can be sampled with high precision by the series and parallel configuration of multiple sampling resistors. The combination of sampling resistors forms a voltage dividing circuit, which can effectively filter out some high-frequency noise or fluctuations, reduce the influence of external interference, and thus improve the stability and reliability of the voltage signal.

[0066] In some embodiments, the first equivalent impedance module 43 includes a first common-mode resistor 431 equivalent to the impedance of the load unit 412, and a first common-mode capacitor 432 equivalent to the impedance of the inverter unit 411; the input end of the first common-mode resistor 431 is connected to the input end of the first common-mode capacitor 432, and the output end of the first common-mode resistor 431 is connected to the output end of the first common-mode capacitor 432.

[0067] In the embodiment of the present application, the first equivalent impedance module 43 realizes impedance matching between the load unit 412 and the inverter unit 411. By adjusting the values of the first common-mode resistor 431 and the first common-mode capacitor 432, the circuit can more efficiently transfer energy during operation, thereby optimizing power output. Impedance matching can reduce power loss and ensure stable operation of the system.

[0068] The above Figure 4 The noise suppression circuit provided adopts a common-mode voltage sampling and compensation mechanism to suppress the common-mode current (EMI noise) generated by the load unit 412 and the inverter unit 411, and realizes the suppression or cancellation of the common-mode current by injecting a reverse first compensation current signal. The following describes the entire compensation mechanism. Figure 4 The entire compensation mechanism is described.

[0069] In the above Figure 4In this circuit, the Direct Current Busbar (DC Bus) contains a positive terminal (Bus+) and a negative terminal (Bus-), used to provide a stable DC input voltage. The DC bus capacitor (C) bus Connected in parallel to the DC bus, it is used to filter out ripples in the DC bus voltage and maintain the stability of the DC bus voltage. The inverter unit 411 generates an AC voltage based on the filtered DC input voltage to drive the load unit 412.

[0070] Optionally, the inverter unit 411 can be composed of six switching devices, two switching devices per phase, with U, V, and W being the three-phase output terminals. The voltage value of the noise voltage generated by the first noise module 41 can be expressed as... Among them, U U U V and U W This represents the three-phase voltage of the first noise module 41, i.e., the noise voltage V. cm The magnitude is the average of the three-phase voltages. For ease of subsequent processing, the noise voltage of the first noise module 41 is sampled through a resistor divider network (first voltage sampling module 42). The output voltage value of the first voltage sampling module 42 can be expressed as V. sen And it has the following proportional relationship with the noise voltage: V sen =k·V cm Where k is the voltage division coefficient, and its value is determined by the resistance value of the first voltage sampling module 42. By selecting an appropriate resistor voltage division ratio, the sampled common-mode voltage, i.e., the voltage value V of the first sampled voltage signal, can be ensured. sen Within the input voltage range of the operational amplifier, overvoltage or undervoltage conditions should be avoided. The voltage divider factor k can be expressed as: Wherein, R1, R2, R3, R4, and R5 are the resistance values ​​of the first sampling resistor SR1, the second sampling resistor SR2, the third sampling resistor SR3, the fourth sampling resistor SR4, and the fifth sampling resistor SR5, respectively. Optionally, the resistance values ​​of the first sampling resistor SR1, the second sampling resistor SR2, and the third sampling resistor SR3 can be equal. By appropriately selecting resistors and adjusting the voltage division coefficient k, the output first voltage signal can be controlled within the normal operating range of the operational amplifier unit 441.

[0071] Optionally, the first protection module 45 includes a first operational amplifier U. 1B First operational amplifier U 1B As a voltage follower (buffer), it provides a low-impedance output to prevent subsequent circuitry from causing a load effect on the first voltage sampling module 42. In other words, the first protection module 45 ensures the voltage value V of the first sampled voltage signal is protected. senIt will not change due to load influence, thus improving the stability of the active EMI filter operation. The voltage value V of the first follower voltage signal output by the first protection module 45. in The voltage value V of the first sampled voltage signal sen Similarly, the first follow-up voltage signal is transmitted to the subsequent circuitry.

[0072] Optionally, the operational amplifier unit 441 includes a second operational amplifier U. 1A Second operational amplifier U 1A Together with its matching first equivalent impedance module 43, a voltage inverter is formed. The function of this voltage inverter is to convert the common-mode voltage into a reverse common-mode current. Therefore, the artificially fitted impedance network (i.e., the first equivalent impedance module 43) includes an equivalent first common-mode resistor 431 with the load unit 412, with a resistance value of Z. motor And a first common-mode capacitor 432, which is equivalent to the impedance of the inverter unit 411, with a resistance value of Z. Cp The impedance signal provided by the artificially fitted impedance network, i.e., the resistance value of the first resistance signal, can be expressed as Z. a =Z motor / / Z Cp

[0073] The first sampled voltage signal, after being scaled down, is transmitted to the first equivalent impedance module 43. The current compensation module 44 can then adjust the current based on the voltage value V of the first sampled voltage signal. sen (or V) in The resistance value Z of the first resistor signal. a Calculate the current value I of the first compensated current signal. inj Specifically, based on the virtual short principle of the operational amplifier, the current I flowing through the first equivalent impedance module 43... in With noise voltage V cm The following relationship exists between them:

[0074] I in =k·V cm Z a

[0075] Through operational amplifier U 1A The inverting amplification effect results in an output voltage signal with the magnitude of: Vo = - R f ·V cm ·Z a Among them, R f This involves adjusting the resistance value of resistor 443. Furthermore, the magnitude I of the first compensation current signal... inj It can be calculated using the following formula:

[0076]

[0077] wherein, Z LISN is the resistance value of the noise detection module (not shown in the figure), which can include a line impedance stabilization network (LISN) for testing and measuring electromagnetic interference (EMI) generated by the device on the power line. Z a is the size of the first resistance signal provided by the first equivalent impedance module 43, Z inj is the resistance value of the output resistor 444. The above direct current blocking unit 445 mainly plays a role in blocking direct current, and in the frequency range of EMI noise, the impedance of the direct current blocking unit 445 can be approximately ignored.

[0078] Further, make Z inj > > Z LISN || Z a , then the size of the first compensation current signal can be approximately expressed as:

[0079]

[0080] In actual use, by selecting appropriate parameters, the first compensation current can effectively offset the common-mode current I cm . Specifically, the size of the adjustment resistor 443 R f and the resistance value of the output resistor 444 Z inj can be set to achieve complete offset of the common-mode current I cm . The final injected first compensation current is equal in size and opposite in direction to the common-mode current, thereby achieving the purpose of common-mode current compensation, reducing EMI noise, and the specific compensation relationship can be expressed as: I inj = - I cm .

[0081] The following describes the test and fitting process of the common-mode impedance of the load unit 412 and the inverter unit 411 to the ground, respectively.

[0082] Figure 5 The structure schematic diagram of a test circuit provided by an exemplary embodiment of the present application is shown in FIG. 1, which includes a load unit 412, an inverter unit 411, a first equivalent impedance module 43, a second equivalent impedance module 44, an adjustment resistor 443, an output resistor 444, and a common-mode current detection module 45. Figure 5As shown, the common mode impedance between the load unit 412 and ground can be obtained by directly shorting the output cable of the three-phase bridge leg (U, V, W) mid-point (V) and testing the common mode impedance between the load unit 412 and ground using an impedance analyzer. Further, an impedance curve similar to the actual test result can be fitted by using RLC components (i.e. a combination of resistance, inductance and capacitance). Thus, the common mode impedance between the load unit 412 and ground can be simulated more accurately, and the design of the noise suppression circuit can be further optimized.

[0083] Figure 6 Another test circuit configuration is provided for an exemplary embodiment of the present application, which can be used to accurately test the common mode impedance of the three-phase bridge leg mid-point of the inverter unit 411 and the printed circuit board (PCB) trace to ground. As shown, the circuit configuration can be used to accurately test the common mode impedance. Specifically, the capacitance between BUS+ and BUS- on the PCB is first removed to ensure that no additional capacitance interferes with the test result. Then, the three terminals of the inverter output are shorted to eliminate any possible interference signals and ensure that the measured common mode impedance only reflects the electrical characteristics between the bridge leg output and the chassis. Thus, the common mode impedance of the inverter unit 411 to ground (chassis) can be measured. During the actual test, the obtained common mode impedance usually varies with frequency, and a capacitor can be used to fit the test results to generate an impedance curve similar to the actual test result. Figure 6

[0084] Figure 7 A common mode impedance characteristic diagram is provided for an exemplary embodiment of the present application. According to the frequency range of the active EMI (electromagnetic interference) filter (AEF), the effective frequency band is usually 150 kHz to 5 MHz. Within this frequency band, the impedance characteristics of the motor and cable to ground exhibit different frequency responses. As shown, the impedance of the motor to ground is relatively low and almost constant within the frequency range. However, the impedance of the cable to ground is relatively high and varies with frequency. Thus, the impedance of the motor to ground is much lower than the impedance of the cable to ground within the frequency range. Figure 7 ​As shown, the impedance characteristics obtained from the test demonstrate the frequency-dependent variation of the impedance of load unit 412 to ground. In the low-frequency range (C), the impedance of load unit 412 to ground exhibits capacitive characteristics, meaning that the impedance increases as the frequency decreases. At a specific frequency, at the first resonant point (LC series resonance), the impedance of load unit 412 exhibits inductive characteristics, and the interaction between the inductor and capacitor forms an LC series resonant point (fr1). Near this frequency, the circuit impedance reaches its minimum value. Next, at the second resonant point (fr2), the impedance curve exhibits the characteristics of a parallel circuit, meaning that the impedance of load unit 412 to ground reaches its maximum value near this frequency and exhibits the characteristics of parallel LC resonance. When the frequency exceeds the second resonant point (f>fr2), the impedance curve again exhibits capacitive characteristics, i.e., the dominance of the capacitor on the impedance increases. Finally, at the third resonant point (f>fr3), the impedance curve again exhibits inductive characteristics, indicating that the impedance of load unit 412 is again dominated by inductance. Based on the above characteristics, the following can be used... Figure 8 The circuit model shown fits the common-mode impedance of load cell 412 to ground. This circuit includes multiple RLC elements (inductor L1, inductor L2, resistor R...). a1 Resistance R a2 Resistance R a1 Resistance R b2 Capacitors C1, C2, and C3 can be used to simulate the impedance characteristics of motors and cables. Furthermore, Figure 9 The simplified circuit shown (including inductor L) s1 Inductor L s2 Capacitor C s1 Capacitor C s2 Resistance R s1 and resistance R s2 It can also be used to simulate the common-mode impedance of load cell 412 to ground. The simplified circuit reduces the number of components, but still effectively reflects the impedance characteristics between load cell 412 and ground, making it suitable for simplified electromagnetic compatibility analysis and design.

[0085] Figure 10 This is a schematic diagram of a noise suppression circuit with multiple noise sources, provided as an exemplary embodiment of this application. Figure 10 As shown, the noise suppression circuit includes: a first noise module 101, a first voltage sampling module 102, a first equivalent impedance module 103, a current compensation module 104, a first protection module 105, a second noise module 106, a second voltage sampling module 107, a second equivalent impedance module 108, and a second protection module 109.

[0086] The input end of the second noise module 106 is connected with the input end of the second voltage sampling module 107, the output end of the second noise module 106 is connected with the output end of the second voltage sampling module 107, the input end of the second voltage sampling module 107 receives the input voltage, the output end of the second voltage sampling module 107 is connected with the input end of the second equivalent impedance module 108, the output end of the second equivalent impedance module 108 is connected with the input end of the current compensation module 104, and the signal end of the current compensation module is connected with the signal end of the second voltage sampling module 107. The connection relationship of other modules is consistent with the above. Figure 4 The connection relationship of other modules is consistent with the above.

[0087] In the noise suppression circuit of multiple noise sources, corresponding voltage sampling modules, protection modules and equivalent impedance modules are added for each noise source. Since each noise source (such as the first noise module and the second noise module) has an independent voltage sampling module and an equivalent impedance module, they can provide compensation signals for different noise sources respectively, avoiding the influence of the compensation of one noise source on another noise source. Therefore, the noise suppression circuit can more accurately suppress the interference of each noise source.

[0088] In some embodiments, the second noise module 106 works according to the input voltage;

[0089] The second voltage sampling module 107 is used for detecting the second sampling voltage signal of the second noise module 106, and sending the second sampling voltage signal to the current compensation module 104 through the signal end of the second voltage sampling module 107.

[0090] The second equivalent impedance module 108 provides a second resistance signal equivalent to the resistance value of the second noise module 106 for the current compensation module 104.

[0091] The current compensation module 104 determines the current value of the second compensation current signal according to the voltage value of the first sampling voltage signal, the voltage value of the second sampling voltage signal, the resistance value of the first resistance signal and the resistance value of the second resistance signal, and sends the second compensation current signal to the first noise module 101 and the second noise module 106 to reduce the noise generated when the first noise module 101 and the second noise module 106 work.

[0092] In the noise suppression circuit of multiple noise sources, the structure and function of the second noise module 106 are consistent with those of the first noise module 101, the structure and function of the second voltage sampling module 107 are consistent with those of the first voltage sampling module 102, the structure and function of the second protection module 109 are consistent with those of the first protection module 105, and the structure and function of the second equivalent impedance module 108 are consistent with those of the first equivalent impedance module 103. Here, no further description is given.

[0093] The aboveFigure 10 For the noise suppression circuit for multiple noise sources, in a system containing multiple noise sources (such as fans, compressors, etc.), by adding a voltage sampling module for each noise source (such as the first noise module 101 and the second noise module 106), the corresponding noise voltage of each noise source is collected, and the corresponding fitting resistance network (the first equivalent impedance module 103 and the second equivalent impedance module 108) is used to match the characteristic impedance of each noise source. Through fine adjustment, the common-mode noise generated by different noise sources can be effectively suppressed, so as to improve the noise suppression capability of the multi-noise source system without greatly increasing the system cost.

[0094] In some embodiments, the noise suppression circuit provided by the present application can be applied to household appliances (such as air conditioners, refrigerators, etc.), communication equipment, and industrial automation equipment. Next, taking an air conditioner as an example, the application of the noise suppression circuit is described.

[0095] Figure 11 An exemplary embodiment of the present application provides a structure diagram of an air conditioner system. As shown in the figure, Figure 11 The air conditioner system includes a first noise module 111, a first voltage sampling module 112, a first equivalent impedance module 113, a current compensation module 114, an input module 115, a line impedance stabilization module 116, a passive filter module 117, and a rectifier module 118. The output end of the input module 115 is connected to the input end of the line impedance stabilization module 116, the output end of the line impedance stabilization module 116 is connected to the input end of the passive filter module 117, the output end of the passive filter module 117 is connected to the input end of the rectifier module 118, and the output end of the rectifier module 118 is connected to the input end of the first voltage sampling module.

[0096] The input module 115 is used to provide AC voltage for the entire air conditioner system to ensure system power supply. The line impedance stabilization module 116 is used to balance the impedance of the power supply line to stabilize the current flow in the power system and reduce power loss. The passive filter module 117 is used to filter out high-frequency noise and harmonics in the input module 115 to improve power quality. The rectifier module 118 is used to convert AC power supply to DC power supply to provide stable DC voltage for the subsequent first noise module 111 and first voltage sampling module. These modules work together to enable the air conditioner system to operate stably and efficiently, reduce power supply interference, and improve the overall performance and reliability of the air conditioner system.

[0097] Further, based on the structure diagram of the air conditioner system provided above Figure 11 The simulation diagram can be constructed based on the structure diagram of the air conditioner system provided above. Optionally, the power supply can use ±12V (volts) as an auxiliary power supply to provide stable operating voltage for the operational amplifier and the push-pull output stage. Based on the simulation diagram, the simulation results can be obtained and analyzed.Figure 12 The schematic diagram of the first simulation result provided for an exemplary embodiment of the present application, Figure 12 demonstrates the dynamic waveforms of the common-mode current signal (I cm ) generated by the noise source, the first compensation current signal (I inj ) and the detection noise current signal (I LISN ) detected by the noise detection module under the action of the active filter. It can be seen from the waveform comparison that the amplitude and high-frequency component of the noise current signal detected by the noise detection module are significantly reduced under the action of the active filter. Figure 13 The schematic diagram of the second simulation result provided for an exemplary embodiment of the present application, Figure 13 It can be seen that the common-mode current signal (I cm ) generated by the noise source and the first compensation current signal (I inj ) have an obvious cancellation relationship in the time domain, and the noise current signal detected by the noise detection module is close to zero after the action of the filter, indicating that the active filter effectively suppresses most of the high-frequency components. Figure 14 The schematic diagram of the third simulation result provided for an exemplary embodiment of the present application, Figure 14 demonstrates the suppression effect of the active filter on the common-mode noise signal, and verifies the noise attenuation performance thereof from the frequency domain. Specifically, in the frequency range of 150kHz-5MHz, the curve of the first sampling voltage signal (V cm ) after the filtering process of the noise suppression circuit has a significant drop compared with the curve of the common-mode noise voltage signal (V LISN ) without the filtering process of the noise suppression circuit, which indicates that the noise suppression circuit has a significant attenuation effect on the common-mode noise in this frequency band.

[0098] The simulation results in the above Figure 12 , Figure 13 and Figure 14 indicate that the active filter provided by the present application containing the noise suppression circuit can effectively compensate the high-frequency common-mode noise current generated by the noise source, thereby significantly reducing the conducted noise of EMI.

[0099] The noise suppression circuit provided by the embodiments of the present application includes a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; the compensation current is adjusted by the current compensation module according to the first sampling voltage signal and the first resistance signal, and the compensation current is injected into the first voltage sampling module, so as to perform corresponding current compensation before or at the initial stage of noise generation through the feedforward control technology, thereby effectively reducing the noise generated when the first noise module works. And the current compensation is directly performed through voltage sampling and signal processing, without the traditional current transformer, thereby reducing the volume, complexity and cost of the noise suppression circuit.

[0100] The application further provides an air conditioning device, comprising the noise suppression circuit.

[0101] The above-mentioned embodiments are merely preferred embodiments of the application, and are not intended to limit the scope of the application. Without departing from the design spirit of the application, various modifications and improvements to the technical solutions of the application made by those skilled in the art shall fall within the protection scope of the claims of the application.

Claims

1. A noise suppression circuit, characterized by, The noise suppression circuit comprises: a first noise module, a first voltage sampling module, a first equivalent impedance module and a current compensation module; an input end of the first voltage sampling module receives an input voltage, an input end of the first noise module is connected with the input end of the first voltage sampling module, and the first noise module works according to the input voltage; an output end of the first noise module is connected with an output end of the first voltage sampling module, a signal end of the first voltage sampling module is connected with a signal end of the current compensation module, the first voltage sampling module detects a first sampling voltage signal of the first noise module, and sends the first sampling voltage signal to the current compensation module through the signal end of the first voltage sampling module; an input end of the first equivalent impedance module is connected with the output end of the first voltage sampling module, and an output end of the first equivalent impedance module is connected with an input end of the current compensation module, the first equivalent impedance module provides a first resistance signal with a resistance value equivalent to that of the first noise module for the current compensation module; an output end of the current compensation module is connected with the input end of the first noise module, the current compensation module determines a current value of a first compensation current signal according to a voltage value of the first sampling voltage signal and a resistance value of the first resistance signal, and sends the first compensation current signal to the first noise module to reduce noise generated when the first noise module works.

2. The noise suppression circuit of claim 1, wherein, The current compensation module comprises an operational amplifier unit, a push-pull unit, an adjusting resistance and an output resistance. A first pin of the operational amplifier unit is connected with a positive pole of a voltage source, a second pin of the operational amplifier unit is connected with a negative pole of the voltage source, and the voltage source provides a driving voltage for the operational amplifier unit; a non-inverting input end of the operational amplifier unit is connected with an output end of the first equivalent impedance module, a same-phase input end of the operational amplifier unit is connected with a ground wire, a first end of the adjusting resistance is connected with the non-inverting input end of the operational amplifier unit, a second end of the adjusting resistance is connected with a first end of the output resistance, and the operational amplifier unit and the adjusting resistance perform inverting and amplifying processing on the first sampling voltage signal based on the first resistance signal to obtain an output voltage signal; an output end of the operational amplifier unit is connected with an input end of the push-pull unit, the push-pull unit enhances an initial compensation current signal based on the output voltage signal and the output resistance to obtain the first compensation current signal with a current value meeting a preset condition; a first end of the output resistance is connected with an output end of the push-pull unit, and a second end of the output resistance is connected with the input end of the first noise module, and the output resistance sends the first compensation current signal to the first noise module through the output end of the current compensation module.

3. The noise suppression circuit of claim 2, wherein, The current compensation module further comprises a direct-current isolation unit; a first end of the direct-current isolation unit is connected with the second end of the output resistance, and a second end of the direct-current isolation unit is connected with the input end of the first noise module.

4. The noise suppression circuit of claim 2, wherein, The push-pull unit comprises a first diode, a second diode, a first resistor, a second resistor, a third resistor, a fourth resistor, a first triode and a second triode; The output end of the operational amplifier unit is connected with the negative electrode of the first diode, the positive electrode of the first diode is connected with the first end of the first resistor, the second end of the first resistor is connected with the positive electrode of the voltage source, the positive electrode of the first diode is connected with the base of the first triode, the collector of the first triode is connected with the positive electrode of the voltage source, the emitter of the first triode is connected with the first end of the second resistor, and the second end of the second resistor is connected with the first end of the output resistor; The output end of the operational amplifier unit is connected with the positive electrode of the second diode, the first end of the third resistor is connected with the negative electrode of the second diode, the second end of the third resistor is connected with the negative electrode of the voltage source, the negative electrode of the second diode is connected with the base of the second triode, the emitter of the second triode is connected with the negative electrode of the voltage source, the collector of the second triode is connected with the first end of the fourth resistor, and the second end of the fourth resistor is connected with the first end of the output resistor.

5. The noise suppression circuit of claim 2, wherein, The noise suppression circuit further comprises a first protection module; The output end of the first noise module is connected with the input end of the first equivalent impedance module through the first protection module; The first protection module follows the first sampling voltage signal output by the first voltage sampling module to obtain a first follow-up voltage signal with a voltage value equal to that of the first sampling voltage signal, so as to protect the first voltage sampling module.

6. The noise suppression circuit of claim 1, wherein, The first noise module comprises an inverter unit and a load unit, the inverter unit comprises a three-phase bridge arm, and the load unit comprises a three-phase winding; The three output ends of the three-phase bridge arm are respectively connected with the three-phase winding; The inverter unit drives the load unit to operate.

7. The noise suppression circuit of claim 6, wherein, The first voltage sampling module comprises a first sampling resistor, a second sampling resistor, a third sampling resistor, a fourth sampling resistor and a fifth sampling resistor; The three-phase winding is respectively connected with the first end of the first sampling resistor, the first end of the second sampling resistor and the first end of the third sampling resistor; The second end of the first sampling resistor, the second end of the second sampling resistor and the second end of the third sampling resistor are all connected with the first end of the fourth sampling resistor, the second end of the fourth sampling resistor is connected with the first end of the fifth sampling resistor, and the second end of the fifth sampling resistor is connected with the ground wire.

8. The noise suppression circuit of claim 6, wherein, The first equivalent impedance module comprises a first common-mode resistor equivalent to the impedance of the load unit and a first common-mode capacitor equivalent to the impedance of the inverter unit; The input end of the first common-mode resistor is connected with the input end of the first common-mode capacitor, and the output end of the first common-mode resistor is connected with the output end of the first common-mode capacitor.

9. The noise suppression circuit of claim 2, wherein, The noise suppression circuit further comprises a second noise module, a second voltage sampling module and a second equivalent impedance module; An input end of the second voltage sampling module receives an input voltage, an input end of the second noise module is connected with the input end of the second voltage sampling module, and the second noise module works according to the input voltage; An output end of the second noise module is connected with an output end of the second voltage sampling module, a signal end of the second voltage sampling module is connected with a signal end of the current compensation module, the second voltage sampling module detects a second sampling voltage signal of the second noise module, and sends the second sampling voltage signal to the current compensation module through the signal end of the second voltage sampling module; An input end of the second equivalent impedance module is connected with the output end of the second voltage sampling module, and an output end of the second equivalent impedance module is connected with an input end of the current compensation module, the second equivalent impedance module provides a second resistance signal with a resistance value equivalent to that of the second noise module for the current compensation module; The current compensation module determines a current value of a second compensation current signal according to a voltage value of the first sampling voltage signal, a voltage value of the second sampling voltage signal, a resistance value of the first resistance signal and a resistance value of the second resistance signal, and sends the second compensation current signal to the first noise module and the second noise module to reduce noise generated when the first noise module and the second noise module work.

10. An air conditioning apparatus characterized by comprising: The noise suppression circuit comprises the noise suppression circuit according to any one of claims 1 to 9.

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